1. Field of the Invention
The present invention relates to a waste heat control apparatus for controlling an amount of waste heat of an engine in accordance with a heat utilization demand.
2. Description of Related Art
Combustion energy generated by fuel combustion in an engine mounted on a vehicle contains a lot of heat energy other than the kinetic energy used to run the vehicle. This heat energy can be used to heat a vehicle cabin, or warm up a catalyst mounted on an exhaust pipe of the engine. For example, it is known to recover engine waste heat contained in engine cooling water, and use the recovered engine waste heat for space heating.
Further, there are proposed various techniques for implementing early warm-up of a catalyst by increasing an exhaust temperature by controlling ignition timing or opening/closing timing of inlet and exhaust valves. For example, refer to Japanese Patent Application Laid-open No. 11-324746.
However, there may occur a case in which the ignition timing or valve opening/closing timings cannot be changed depending on the running state of the engine. In this case, since the exhaust temperature cannot be increased, early warm-up of the catalyst can not be implemented. For example, when the engine is running at low load, since the amount of engine waste heat is small, there may occur a case in which a demanded amount of waste heat cannot be satisfied. Meanwhile, if the ignition timing or valve opening/closing timing is changed regardless of the running state of the engine, the fuel efficiency of the engine may be lowered significantly.